Curved image sensor for a curved focal surface

ABSTRACT

This document describes curved image sensors capable of sensing light from a monocentric lens. This curved image sensor receives light focused at a curved focal surface and then provides electric signals from this curved image sensor to a planar computing chip, such as a CMOS chip. By so doing, the higher image quality, smaller size, and often smaller weight of monocentric lenses can be gained while using generally high-quality, low-cost planar chips.

BACKGROUND

This background description is provided for the purpose of generallypresenting the context of the disclosure. Unless otherwise indicatedherein, material described in this section is neither expressly norimpliedly admitted to be prior art to the present disclosure or theappended claims.

Conventional imaging devices use multi-lens assemblies that provide aflat focal plane. These multi-lens assemblies enable use of planar imagedevices, such as a silicon chip having an integrated array oflight-sensitive photodetectors. These conventional imaging devices,however, have various limitations, such as poor resolution at edges ofthe flat focal plane and a need for highly precise lens alignment in theassembly. The dimensions of the multi-lens assemblies also result in acompromise between image quality and thickness of computing devices thathave the imaging device, such as mobile phones, smaller cameras, andcomputing spectacles. In effect, multi-lens assemblies limit how thin orsmall a device can be when high-quality imaging is desired.

In contrast, monocentric lenses are capable of providing higher opticalresolution across a wide field of view, often at smaller sizes and coststhat multi-lens assemblies. Monocentric lenses, however, produce acurved focal surface rather than the flat focal plane common tomulti-lens assemblies. Because of this, high-quality and low-cost planarcomputing and sensing chips cannot readily be used with monocentriclenses.

BRIEF DESCRIPTION OF THE DRAWINGS

Apparatuses of and techniques using a curved image sensor for a curvedfocal surface are described with reference to the following drawings.The same numbers are used throughout the drawings to reference likefeatures and components:

FIG. 1 illustrates an example environment in which a curved image sensorfor a curved focal surface can be enabled.

FIG. 2 illustrates optical properties of a monocentric lens, showinglight from a scene captured by the monocentric lens and, for contrast, atraditional multi-lens assembly having multiple aspherical lenses.

FIG. 3 illustrates the curved image sensor of FIG. 1 in greater detail,including a curved surface, a curved-to-planar substrate, and a circuit.

FIG. 4 illustrates a curved-to-planar substrate in cross-section andplan views, including electric connections to photodetectors on a curvedsurface.

FIG. 5 illustrates the computing device of FIG. 1 in greater detail.

FIG. 6 illustrates example methods that use a curved image sensor and amonocentric lens to capture an image.

FIG. 7 illustrates an image constructed from light sensed from the sceneof FIG. 2.

FIG. 8 illustrates various components of an electronic device that canimplement a curved image sensor for a curved focal surface in accordancewith one or more embodiments.

DETAILED DESCRIPTION

This document describes curved image sensors capable of sensing lightfrom a monocentric lens. This curved image sensor receives light focusedon a curved focal surface and then provides electric signals from thiscurved image sensor to a planar integrated circuit substrate, such as aComplementary Metal-Oxide Semiconductor (CMOS) chip. By so doing, thewider field of view, smaller size, and often smaller weight ofmonocentric lenses can be gained while using generally high-quality,low-cost planar chips.

The following discussion describes an operating environment, examplecurved image sensors for curved focal surfaces, followed by techniquesthat may be employed in this environment, and ending with an exampleelectronic device.

Example Environment

FIG. 1 illustrates an example environment 100 in which a curved imagesensor for a curved focal surface can be embodied. Example environment100 includes a computing device 102 capturing images of a scene 104.Computing device 102 includes an imaging device 106 shown in part at106-1 and in detail at 106-2. Imaging device 106 includes monocentriclens 108 and curved image sensor 110. Ways in which monocentric lens 108operates are described in FIG. 2, followed by a detailed illustration ofcurved image sensor 110 in FIG. 3.

FIG. 2 illustrates optical properties of monocentric lens 108, whichshows light 202 from a scene 204 captured by monocentric lens 108.Monocentric lens 108 focuses this light 202, and thus scene 204, to acurved focal surface 206. Contrast this with multi-lens assembly 208focusing to a flat focal plane 210. Multi-lens assembly 208 is shownwith multiple aspherical lenses, but may include a mix of lenses andother optical elements. While not to scale, multi-lens assembly 208often requires a substantially larger Z-height (in this example theassembly length along the optical axis) than a monocentric lens.Z-heights not only include focal-path dimensions of the lens or lensassembly, shown at monocentric-lens focal path 212 andmulti-lens-assembly focal path 214, but also back-focal distance, shownhere as monocentric-lens back-focal distance 216 and multi-lens-assemblyback-focal distance 218. Thus, monocentric-lens Z-height 220, assumingsimilar image quality, is substantially smaller than multi-lens-assemblyZ-height 222. Note also the complexity in making, configuring, andaligning the seven lens elements of multi-lens assembly 208 and thatmonocentric lens 108 may also have a field of view (e.g., 120 to 180degrees) that is superior to that of multi-lens assembly 208.

While the example shown of monocentric lens 108 is that of a singular,spherical lens, multiple lenses or a non-spherical lens is permitted.Monocentric lenses may have a lens surface that has a common center butneed not be fully spherical. A common center may include a section of asphere, for example. Further, multiple monocentric lenses can be used,which, while it may increase Z-height, the precision needed to alignmonocentric lenses can be lower than aspherical lenses and fewer lensesmay be used than in a multi-lens assembly.

FIG. 3 illustrates curved image sensor 110 of FIG. 1 in greater detail.Curved image sensor 110 includes a curved surface 302, acurved-to-planar substrate 304, and a circuit 306. Curved image sensor110 is shown in cross-section view 308 and in plan view 310. Plan view310 is from a perspective at which an image is captured but without alens being shown (looking down on curved surface 302). Curved surface302 can be surfaced to conform to some section of a sphere, which inturn corresponds to a surface of monocentric lens 108, and, as shown inFIG. 1, surrounds a portion of monocentric lens 108.

Curved surface 302 includes photodetectors 312, which are disposed on orin curved surface 302, and are capable of sensing light at curvedsurface 302. In response to light, photodetectors 312 provide electricsignals at curved surface 302. This illustration shows resolutions ofphotodetectors 312 with hexagons of a particular size, which are hereassumed to be pixels. The number of photodetectors 312 is simplified forvisual clarity, as showing millions of pixels is not possible for thistype of illustration. The varying shades illustrated for photodetectors312 indicate sensitivity to different wavelengths of lights, such asred, green, or blue.

Photodetectors 312 may include an array of deposited photodetectors,which can be non-silicon and be active-pixel photodetectors. Other typesof photodetectors can be used, such as an organic light-sensing materialhaving amorphous sensing areas capable of spatially-coherently detectinglight and converting the light into the electric signals. This materialmay be one or multiple layers, such as with three layers each of whichis sensitive to a light of a different wavelength. Note that someorganic light-sensing materials generate a charge (e.g., an electricsignal) sufficient for an electrical conductor to carry the charge(e.g., sense) without neighboring conductors doing the same, as someorganic materials have a high conductivity in a perpendicular direction(e.g., perpendicular to curved surface 302) and a low conductivity in aparallel direction (e.g., parallel to curved surface 302). Amorphousareas are approximated by hexagons shown at photodetectors 312, thoughthis is for illustration purposes only.

Still other types of photodetectors 312 can be on or in curved surface302, including quantum-dot photodetectors. Quantum-dot photodetectorsproduce an electronic signal when excited by visible (and in some casesnon-visible) light. They are generally a nanocrystal made of asemiconductor material and which is small enough to exhibit quantumcharacteristics. One potential advantage to quantum-dot photodetectorsis that they can be applied to curved surfaces and, in some cases, beapplied over electrical conductors, such as to electrical connectionsends illustrated below. Quantum-dot photodetectors can be disposed oncurved surface 302 as groups of dots or layers of dots, each of thegroups or layers acting as one or more of photodetectors 312.Photodetectors 312 may also include photodetective materials sensitiveto the infrared spectrum, such as indium gallium arsenide (InGaAs),indium arsenide or monoarsenide (InAs, a semiconductor), or indiumantimonide (InSb). Some quantum dots can be formed from a monolayer ofindium arsenide on indium phosphide or gallium arsenide, or from a layerof indium gallium arsenide. Also, indium antimonide can be grown fromorganometallic compounds using chemical vapor deposition (e.g.,matalorganic vapor-phase epitaxy, deposited on curved surface 302).Infrared-spectrum sensitivity can be used for thermal imaging andimproved low-light imaging, alone or in combination with photodetectorssensitive to visible light.

Curved-to-planar substrate 304 is capable of receiving electric signalsat curved surface 302 and providing the electric signals to a planarsurface, such as circuit 306. In some cases curved-to-planar substrate304 is a dense arrangement of electric connectors within an insulatingmedium. These electric connectors can connect, such as through wires(e.g., metal or nanotube), electric signals from photodetectors oncurved surface 302 to circuit 306. As noted above, a high-quality andrelatively inexpensive CMOS chip (e.g., one configured to read electricsignals from a photodetector array) can be used. This CMOS chip can besimilar to some current CMOS sensors, though with the actualphotodetectors not placed on the chip. Instead, electrical receptors areon a planar surface or substrate of the chip, which can be connected viacurved-to-planar substrate 304 to photodetectors of curved surface 302.Curved image sensor 110 can be an integrated device havingphotodetectors 312 on curved surface 302, curved-to-planar substrate304, and circuit 306.

In more detail, consider curved-to-planar substrate 304 as illustratedin FIG. 4 in cross-section view 402 and plan view 404. Curved-to-planarsubstrate 304 includes electric connections 406 to each sensor 312 (orsensor area or region) on curved surface 302. Each of electricconnections 406 connect photodetectors electrically to circuit 306 viaelectric receptors 408. Note that in this example an organic layer 410of sensing material is shown, rather than hexagonal photodetectors, withcurved-surface electric connection ends 412 shown in plan view 404(which may or may not be visible through organic layer 410).

As noted in part above, circuit 306 is capable of receiving electricsignals at a planar surface and from the curved-to-planar substrate.Examples of this reception are through electric receptors 408 withincircuit 306, received through electric connections 406, which in turnreceive the electric signals from photodetectors 312 at curved surface302 and through curved-surface electric connection ends 412.

In some cases, circuit 306 includes a regular array of electricreceptors, such as in cases where circuit 306 is a CMOS chip designedfor an array of photodetectors but does not include thosephotodetectors. In such a case, electric receptors 408 may be in aregular array that is not spatially consistent with electric connections406 at curved surface 302. Thus, curved-to-planar substrate 304 mayinclude electric connections that are non-vertical or are arranged toconnect an irregular array of photodetectors (and thus curved-surfaceelectric connections ends 412) to a regular or otherwise differing arrayof connections. This can enable use of less expensive, less customized,and/or denser circuits. Note that the plane described for circuit 306may include a rough approximation of a plane or multiple planes, such asa roughly planar surface having steps on circuit 306.

Having generally described curved image sensors for curved focalsurfaces and imagers, this discussion now turns to FIG. 5, whichillustrates computing device 102 of FIG. 1 in greater detail. Computingdevice 102 is illustrated with various non-limiting example devices:smartphone 102-1, laptop 102-2, television 102-3, desktop 102-4, tablet102-5, camera 102-6, security system 102-7, and computing spectacles102-8. Computing device 102 includes processor(s) 504 andcomputer-readable media 506, which includes memory media 508 and storagemedia 510. Applications and/or an operating system (not shown) embodiedas computer-readable instructions on computer-readable memory 506 can beexecuted by processor(s) 504 to provide some of the functionalitiesdescribed herein. Computer-readable media 506 also includes imagemanager 512 (described below). As noted in FIG. 1, computing device 102includes imager 106, which in turn includes monocentric lens 108 andcurved image sensor 110.

Computing device 102 may also include network interface(s) 514 forcommunicating data over wired, wireless, or optical networks. By way ofexample and not limitation, network interface 514 may communicate dataover a local-area-network (LAN), a wireless local-area-network (WLAN), apersonal-area-network (PAN), a wide-area-network (WAN), an intranet, theInternet, a peer-to-peer network, point-to-point network, a meshnetwork, and the like.

Example Method

The following discussion describes a method by which techniques areimplemented to enable use of a curved image sensor for a curved focalsurface. This method can be implemented utilizing the previouslydescribed environment and example photodetectors, substrates, andcircuits, such as those shown in FIGS. 1-5. Aspects of this method isillustrated in FIG. 6, which is shown as operations performed by one ormore entities.

FIG. 6 illustrates method 600, which uses a curved image sensor alongwith a monocentric lens to capture an image. At 602, light that isreceived is focused to a curved focal surface by at least onemonocentric lens. This light is received at a curved image sensor inwhich photodetectors are disposed on a curved surface. By way ofexample, assume that light from scene 204 of FIG. 2 is received bymonocentric lens 108 of FIGS. 1 and 2.

At 604, the received light is converted to electric signals through thephotodetectors disposed on the curved surface of the curved imagesensor. The curved surface may be configured in any suitable way, suchas including photodetectors that produce electric signals in response toexposure to light of one or more wavelengths. Continuing the ongoingexample, the light from scene 204 is focused at curved focal surface 206and sensed, by photodetectors 312 of FIG. 3, effective to produceelectric signals.

At 606, the electric signals are passed through a curved-to-planarsubstrate from the curved surface to a circuit. Thus, electric signalscorresponding to colors and color intensity sensed by photodetectors 312are passed from curved-surface electric connection ends 412, throughelectric connections 406, and to electric receptors 408 on circuit 306,as shown in FIG. 4.

At 608, an image is constructed from the electric signals received atthe circuit. Thus, circuit 306, alone or in combination with hardware,firmware, or software elements, constructs an image of scene 104. Imagemanager 512 of FIG. 5 may process or post-process the electric signalsrepresenting the image of scene 104, such as to alter a layout to fit aparticular size (e.g., aspect ratio or frame size). Thus, if a roundscene is captured, image manager 512 may convert the round image to arectangular image for storage and use. Image manager 512 may alsoperform post-processing to improve resolution (e.g., for green, green,red, blue photodetectors in which the green photodetectors are also usedfor sharpness), filtering, and so forth. Circuit 306, however, mayconstruct the image with little or no assistance, such as when anappropriate CMOS chip intended for image processing is used.

Concluding the ongoing example, at 608, circuit 306 and image manager512 construct image 702, illustrated in FIG. 7, from light sensed fromscene 204 of FIG. 2.

Example Electronic Device

FIG. 8 illustrates various components of an example electronic device800 that can be implemented as a computing device having an imager asdescribed with reference to any of the previous FIGS. 1-7. Electronicdevice 800 may be implemented as any one or combination of a fixed ormobile device, in any form of a consumer, computer, portable, user,communication, phone, navigation, gaming, audio, camera, messaging,media playback, and/or other type of electronic device, such ascomputing device 102 described with reference to FIGS. 1 and 5.

Electronic device 800 includes communication transceivers 802 thatenable wired and/or wireless communication of device data 804, such asreceived data, transmitted data, or sensor data as described above.Example communication transceivers include NFC transceivers, WPAN radioscompliant with various IEEE 802.15 (Bluetooth™) standards, WLAN radioscompliant with any of the various IEEE 802.11 (WiFi™) standards, WWAN(3GPP-compliant) radios for cellular telephony, wireless metropolitanarea network (WMAN) radios compliant with various IEEE 802.16 (WiMAX™)standards, and wired local area network (LAN) Ethernet transceivers.

Electronic device 800 may also include one or more data input ports 806via which any type of data, media content, and/or inputs can bereceived, such as user-selectable inputs, messages, music, televisioncontent, recorded video content, and any other type of audio, video,and/or image data received from any content and/or data source (e.g.,other image devices or imagers). Data input ports 806 may include USBports, coaxial cable ports, and other serial or parallel connectors(including internal connectors) for flash memory, DVDs, CDs, and thelike. These data input ports may be used to couple the electronic deviceto components (e.g., imager 106), peripherals, or accessories such askeyboards, microphones, or cameras.

Electronic device 800 includes processor system 808 (e.g., any ofapplication processors, microprocessors, digital-signal-processors,controllers, and the like), or a processor and memory system (e.g.,implemented in a SoC), which process (i.e., execute) computer-executableinstructions to control operation of the device. Processor system 808may be implemented as an application processor, embedded controller,microcontroller, and the like. A processing system may be implemented atleast partially in hardware, which can include components of anintegrated circuit or on-chip system, digital-signal processor (DSP),application-specific integrated circuit (ASIC), field-programmable gatearray (FPGA), a complex programmable logic device (CPLD), and otherimplementations in silicon and/or other hardware.

Alternatively or in addition, electronic device 800 can be implementedwith any one or combination of software, hardware, firmware, or fixedlogic circuitry that is implemented in connection with processing andcontrol circuits, which are generally identified at 810 (processing andcontrol 810). Hardware-only devices in which a curved image sensor for acurved focal surface may be embodied include those that convert, withoutcomputer processors, sensor data into voltage signals.

Although not shown, electronic device 800 can include a system bus,crossbar, or data transfer system that couples the various componentswithin the device. A system bus can include any one or combination ofdifferent bus structures, such as a memory bus or memory controller, aperipheral bus, a universal serial bus, and/or a processor or local busthat utilizes any of a variety of bus architectures.

Electronic device 800 also includes one or more memory devices 812 thatenable data storage, examples of which include random access memory(RAM), non-volatile memory (e.g., read-only memory (ROM), flash memory,EPROM, EEPROM, etc.), and a disk storage device. Memory device(s) 812provide data storage mechanisms to store device data 804, other types ofinformation and/or data (e.g., image 702), and various deviceapplications 814 (e.g., software applications). For example, operatingsystem 816 can be maintained as software instructions within memorydevice 812 and executed by processor system 808. In some aspects, imagemanager 512 is embodied in memory devices 812 of electronic device 800as executable instructions or code. Although represented as a softwareimplementation, image manager 512 may be implemented as any form of acontrol application, software application, signal-processing and controlmodule, or hardware or firmware installed on circuit 306 of imager 106.

Electronic device 800 also includes audio and/or video processing system818 that processes audio data and/or passes through the audio and videodata to audio system 820 and/or to display system 822 (e.g., a screen ofa smart phone or camera). Audio system 820 and/or display system 822 mayinclude any devices that process, display, and/or otherwise renderaudio, video, display, and/or image data. Display data and audio signalscan be communicated to an audio component and/or to a display componentvia an RF (radio frequency) link, S-video link, HDMI (high-definitionmultimedia interface), composite video link, component video link, DVI(digital video interface), analog audio connection, or other similarcommunication link, such as media data port 824. In someimplementations, audio system 820 and/or display system 822 are externalcomponents to electronic device 800. Alternatively or additionally,display system 822 can be an integrated component of the exampleelectronic device, such as part of an integrated touch interface.

Electronic device 800 includes, or has access to, imager 106, whichincludes monocentric lens 108 and curved image sensor 110. Sensor datais received from imager 106 and/or curved image sensor 110 by circuit306 and then image manager 512, here shown stored in memory devices 812,which when executed by processor system 808 constructs a final image asnoted above and shown in FIG. 7.

Although embodiments of a curved image sensor for a curved focal surfacehave been described in language specific to features and/or methods, thesubject of the appended claims is not necessarily limited to thespecific features or methods described. Rather, the specific featuresand methods are disclosed as example implementations a curved imagesensor for a curved focal surface.

What is claimed is:
 1. A curved image sensor comprising: a curvedsurface on which photodetectors are disposed, the photodetectors capableof sensing light at the curved surface and providing, from the curvedsurface, electric signals in response to sensing the light; acurved-to-planar substrate capable of receiving the electric signals atthe curved surface and providing the electric signals to a planarsurface, the curved-to-planar substrate comprising: an array ofelectrical connections for providing the electric signals between thecurved surface and the planar surface, each electrical connection havinga curved-surface connection end and an electric receptor end, thecurved-surface connection ends being irregularly arranged at the curvedsurface and the electric receptor ends being regularly arranged at theplanar surface in a manner such that the electric receptor ends are notspatially consistent with the electric connection ends at the curvedsurface; and a circuit capable of receiving the electric signals at theplanar surface and from the curved-to-planar substrate.
 2. The curvedimage sensor as recited in claim 1, wherein the curved surfacecorresponds to a curved focal surface of a monocentric lens, themonocentric lens disposed at least partially within the curved surface.3. The curved image sensor as recited in claim 1, wherein thephotodetectors disposed on the curved surface comprise a depositedphotodetector array.
 4. The curved image sensor as recited in claim 3,wherein the deposited photodetector array includes active-pixelphotodetectors.
 5. The curved image sensor as recited in claim 1,wherein the photodetectors include an organic light-sensing materialincluding one or more layers having amorphous sensing areas capable ofspatially coherently detecting the light and converting the light intothe electric signals.
 6. The curved image sensor as recited in claim 5,wherein the organic light-sensing material includes three layers, eachof the three layers being sensitive to a different wavelength of light.7. The curved image sensor as recited in claim 5, wherein the amorphoussensing areas have a high conductivity in a direction perpendicular tothe one or more layers and a low conductivity in a direction parallel tothe one or more layers.
 8. The curved image sensor as recited in claim7, wherein the curved-surface connection ends are each connected to arespective one of the amorphous sensing areas.
 9. The curved imagesensor as recited in claim 1, wherein the photodetectors are quantum-dotphotodetectors capable of sensing the light and producing the electronicsignals in response to the light.
 10. The curved image sensor as recitedin claim 1, wherein the curved surface, the curved-to-planar substrate,and the circuit are integrated within a single die or substrate.
 11. Thecurved image sensor as recited in claim 1, wherein a spacing between thecurved-surface connection ends on the curved surface decreases as thedistance from a center of the curved-to-planar substrate increases. 12.The curved image sensor as recited in claim 1, wherein the electricreceptor ends on the planar surface are in a regular array.
 13. A methodcomprising: receiving, at a curved image sensor in which photodetectorsare disposed on a curved surface, light focused to a curved focalsurface by at least one monocentric lens; converting the light toelectric signals through the photodetectors disposed on the curvedsurface of the curved image sensor; passing the electric signals througha curved-to-planar substrate from the curved surface to a circuit, thecurved-to-planar substrate comprising: an array of electricalconnections for providing the electric signals between the curvedsurface and the circuit, each electrical connection having acurved-surface connection end and an electric receptor, thecurved-surface connection ends being irregularly arranged at the curvedsurface and the electric receptors being regularly arranged at thecircuit in a manner such that the electric receptor ends are notspatially consistent with the electric connection ends at the curvedsurface; and constructing an image from the electric signals received atthe circuit.
 14. The method as recited in claim 13, wherein the circuitis a planar Complementary Metal-Oxide Silicon (CMOS) chip andconstructing the image is performed by the planar CMOS chip.
 15. Themethod as recited in claim 13, wherein the photodetectors disposed onthe curved surface of the curved image sensor includes one or morelayers of organic light-sensing material or include one or more quantumdots or layers of quantum dots.
 16. An imaging device comprising: amonocentric lens capable of providing a curved focal surface; and acurved image sensor, the curved image sensor having: a curved surface; acurved-to-planar substrate; and a circuit, the curved image sensorcapable of sensing light of the curved focal surface at the curvedsurface and providing electric signals in response to sensing the light;the curved-to-planar substrate capable of receiving the electric signalsat the curved surface and providing the electric signals to a planarsurface, the curved-to-planar substrate comprising: an array ofelectrical connections for providing the electric signals between thecurved surface and the planar surface, each electrical connection havinga curved-surface connection end and an electric receptor end, thecurved-surface connection ends being irregularly arranged at the curvedsurface and the electric receptor ends being regularly arranged at theplanar surface in a manner such that the electric receptor ends are notspatially consistent with the electric connection ends at the curvedsurface; and the circuit capable of receiving the electric signals atthe planar surface and from the curved-to-planar substrate.
 17. Theimaging device as recited in claim 16, wherein the curved surface of thecurved image sensor surrounds at least a portion of the monocentriclens.
 18. The imaging device as recited in claim 16, wherein themonocentric lens is spherical and the curved surface is a portion of asphere.
 19. The imaging device as recited in claim 16, wherein thecurved surface includes an array of the photodetectors and the circuitis a Complementary Metal-Oxide Silicon (CMOS) chip configured to readthe electric signals of the array received via the curved-to-planarsubstrate.
 20. The imaging device as recited in claim 16, furthercomprising: one or more computer processors; and one or morecomputer-readable storage media having instructions stored thereon that,responsive to execution by the one or more computer processors, performsoperations comprising: constructing an image from the electric signalsreceived at the circuit, the image corresponding to the light of thecurved focal surface; and providing the image.